Initiator



P 1932 H. A. LEWIS 1,877,772

INITIATQR Filed April 24, 1931 Fig.3

H arold ALewis, INVENTOR Patented Sept. 20, 1932 UNITED. STATES PATENT- OFFICE HAROLD A, LEWIS, 0F WOODIBURY, NEW JERSEY, ASSIGNOR TO E. I. DU POINT DE NEMOURS & COMPANY, OF WILMINGTON, DELAWARE, A CORPORATION OF DELA- WARE INITIATOB Application filed April 24,

This invention relates to initiators for high explosives and more particularly tolead azide blasting caps and the like, and comprises a treated steel alloy shell in combination With an explosive charge for the same.

Blasting caps as heretofore manufactured have usually comprised a shell of gilding metal (copper-zinc) or aluminum, or its alloys. By the term blasting caps as used herein I means to include either a fuse or ordinary cap, an electric blasting cap, and/or a delay electric blasting cap. Descriptions of each type follow hereinafter. Blasting caps having mercury fulminate as the main charge or as a priming agent have usually en constructed of gilding metal, because of I .e compatibility of mercury fulminate With 7 .ch copper alloys. Caps containing lead :ide have usually been made of aluminum or its alloys, since this compound incombination with copper or copper alloys forms supersensitive copper azide, particularly in the presence of moisture and carbon dioxide, thus making such combinations hazardous and prohibitive. Furthermore, it has been found that aluminum-shell, lead-azide primed caps give off an excessive flash upon detonation, probably because of the combustion rife the aluminum shell. This flash is frequently suflic'ient in intensity to ignite inflammable gases, such as are present in gaseous coal mines, thus making this type of shell also hazardous and prohibitive.

Detonators for high explosive shells and priming cups for small arms ammunition have also commonly'been made of gilding metal, of brass, or of copper-nickel alloys. Besides excessive costof such shells and other parts made of these metals, they have had.

other inherent disadvantages.

There are other disadvantages -in both aluminum and copper blasting ca s, aside from cost and non-uniformity of orm and composition, in that when either is usedfor blasting in the mining of salt, the fine metal 1931. Serial N0. 532,472.

particles that result are generally objectionable in the salt and render the salt unsatisfactory for many purposes. For example, when such salt is used in tanning processes, a discoloration of the, hides invariably results. Furthermore, when these types of blasting caps are used in connection with the blasting of coal, any unexploded caps later present a serious hazard in the subsequent use of the coal. In either case, neither the particles nor the unexploded caps can be conveniently removed from the mined material by the most suitable means, namely, the magnet, because of the non-magnetic properties of these metals.

Other metals have been suggested for use in the manufacture of blasting caps but have not found application because of various disadvantages.

An object of my invention is to provide an initiator that is universally suitable for all types of firing and blasting operations. A further object of my invention is to provide an initiator, the metallic material of which is compatible with both mercury fulminate and lead azide. Another object of my invention is to provide an initiator which is constructed of less expensive materials than those heretofore known and used. A still further object of my invention is to provide an initiator, and particularly a blasting cap, which is magnetic. Other objects will be apparent as the description proceeds.

These objects are accomplished by the following invention, in which I have found that nitrided steel alloys, when used in combination with mercury fulminate and lead azide, is compatible therewith, yields a roduct that is non-corrosive, does not give 0 an objectionable flash when exploded, and has magnetic properties, besides many other advantages.

The nitrided steel alloy'above mentioned is produced by a nitriding process. By the term nitriding as used herein is meant that process in which the steel alloy is treated at elevated temperatures .with substances which give off nitrogen, such, for example, as ammonia. It is believed that in this process an iron nitride is thus formed on the surface of the metal. By the term steel alloy, as used herein, I mean to include any of the common alloys of steel, which are recognized to take on a definite hardness when nitrided.

. These compriseste els containing 1 to 5 per cent of materials such as copper, aluminum, chromium, manganese, and the like, in addition to the small quantities of the ordinary impurities in iron such as carbon,1')hosphorus, sulfur,'etc.

In carrying out the process, a steel alloy shellis formed in any suitable manner, and heated to an elevated temperature, and ammonia is passed over the shell for a sufiicient period to produce a surface resistant to corrosion. For example, temperatures of 800 to 1200- F, may be advantageously used, and, at these temperatures, periods of time varying from one-half to ten hours may be employed. At these temperatures and time periods, the rate of ammonia passed may be .such that the percentage of decomposition of the ammonia may vary from 5 to 95 per cent, depending upon the surface coating desired.

Upon cooling, a shell is obtained that is very resistant to atmospheric corrosion, and at the same time has the satisfactory properties which make it desirable in a detonator cap or similar combination. Furthermore, I

have found that when the steel alloy shellis annealed before the nitriding process, its brittleness is reduced, and it is less liable to crack\ when crimped upon the fuse. Other methods of nitriding the steel may be used such as heating the caps or shells in anoven in the presence of a nitrogen containing material,

such, for example, as guanidine compounds or other similar compounds that yield nitrogen upon heating.

The nitrided steel alloy shells described herein may be dyed, lacquered, metal coated, or metal plated to improve the appearance, or for the purpose of protection of the shell, and for this purpose a coating is proposed that is compatible with the explosive charges inc'orporated therein. For example, dyes in solution, lacquers containing nitrocellulose,

priming cups suitable for small arms ammunition.

In each of Figures 1, 2i and 3,15. represents a nitrided steel shell which maybe a plain shell or one coated or plated as hereinbefore describedTwB represents a charge of a secondary detonating material, for example tetryl, while 0 represents a charge of a primary detonating compound, for example, of lead azide. 1

In Figure 2, E, F, G, and H, represent the usual elements of an electric blasting cap in which E isadapted to be fired by the bridge e wire H carried by the firing wire G.

Figure 3 represents anelectric blasting cap of the delay type in which the delay element K is substituted for the loose charge E in Figure 2. When fired the burninggases from the relay element may escape through the opening M and may be carried through the outer sleeve N. Elements F, I, J, and L, in Figures 2 and 3 represent a water-proofing and sealing composition. Figures 4 and 5 represent respectively a detonato'r for a high explosive shell and priming cups r small arms ammunition of conventional d'sign.

Whereas I have described my invention as applicable particularly to blasting caps, it will be apparent that it may equally well be applied to primers for ammunition and to detonators for high explosives shells and drop bombs.

Therefore, by the term initiators, used herein, I mean to include blasting caps for use with commercial explosives such as dynamite, detonators for high explosive shells,

depthbombs, hand grenades, and the like, I

and primers for small arms ammunition.

It is to" be understood that the foregoing examples are illustrative only and that other embodiments exist and may be practiced within the scope of my invention. For example, nitrided steel alloy shells may be used in combination with other explosive charges such'as the seriesof so-called straightfulminate detonators. It is to be further understood that I do not intend to be limited in invention-except as indicatedin the following patent claims: I claim e 1. An initiator comprising in combination an explosive charge and a nitridedsteel alloy shell encasing the charge.

2. A blasting cap comprising in combination an explosive charge and a nitrided steel alloy shell encasing the charge.

. 3. A detonator comprising in combination an explosive charge and a nitrided steel alloy shell encasing the charge.

4. priming. cup comprising in combination an explosive charge and a nitrided steel alloy shell encasing the charge.

5. An initiator comprising in combination a charge of a. secondary detonating compound, a charge ,of a primary detonating compound, and a nitrided steel alloy shell encasing the compounds.

6. A blasting cap comprising in combination a charge of a secondary detonatingcompound, a charge of a primary detonating compound and a nitrided "steal alloy shell a charge of a secondary detonating compound, a charge of lead azide and a nitrided steel alloy shell encasing the comp0unds.

10. A blasting cap comprising in combination a charge of a secondary detonating compound, a charge of lead azide, and a nitrided steel alloy shell encasing the compounds.

11. A detonator comprising in combination a charge of asecondary detonating compound, a charge of lead azide and a nitrided steel alloy shell encasing the compounds.

12. A priming cup comprising in combination a charge of a secondary detonating compound, a charge of lead azide and a nitrided steel alloy shell encasing the compounds.

13. An initiator comprising in combination a charge of tetryl, a charge of lead azide, and a nitrided steel alloy shell encasing the charges.

14. A blasting cap comprising in combinationa charge of tetryl, a charge of lead azide, and a nitrided steel alloy shell encasing the charges.

15. A detonator comprising in combination a charge of tetryl, a charge of lead azide, and a nitrided steel alloy shell encasing the charges.

16. A priming cup comprising in combination a charge of tetryl, a, charge of lead azide, and a nitrided steel alloy shell encasing the charges.

17. An initiator comprising in combination an explosive charge and an annealed, nitrided steel alloy shell encasing the charge.

18. A blasting cap comprising in combination an explosive chargeand an annealed, nitrided steel alloy shell encasing the charge.

19. A detonator comprising in combination an explosive charge and an annealed, nitrided steel alloy shell encasing the charge.

20. A priming cu comprising in combmation an explosive c arge and an annealed, nitrided steel alloy shell encasing the charge.

21. An initiator comprising in combination an explosive charge and a nitrided, coated, steel alloy shell encasing the charge.

22. A blasting cap comprising in combination an explosive charge and a nitrided, coated, steel alloy shell encasing the charge.

23. A detonator comprising in combination an explosive charge and a nitrided, coated, steel alloy shell encasing the charge.

24. A priming cup comprising in combination an explosive charge and a nitrided, coated, steel alloy shell encasing the charge.

25. An initiator comprising in combination a charge of lead azide, and a nitrided steel alloy encasing the charge.

In testimony whereof I aflix my signature.

HAROLD A. LEWIS. 

